Unveiling Extreme Anisotropy in Elastic Structured Media

G. Lefebvre, T. Antonakakis, Y. Achaoui, R. V. Craster, S. Guenneau, P. Sebbah

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Periodic structures can be engineered to exhibit unique properties observed at symmetry points, such as zero group velocity, Dirac cones, and saddle points; identifying these and the nature of the associated modes from a direct reading of the dispersion surfaces is not straightforward, especially in three dimensions or at high frequencies when several dispersion surfaces fold back in the Brillouin zone. A recently proposed asymptotic high-frequency homogenization theory is applied to a challenging time-domain experiment with elastic waves in a pinned metallic plate. The prediction of a narrow high-frequency spectral region where the effective medium tensor dramatically switches from positive definite to indefinite is confirmed experimentally; a small frequency shift of the pulse carrier results in two distinct types of highly anisotropic modes. The underlying effective equation mirrors this behavior with a change in form from elliptic to hyperbolic exemplifying the high degree of wave control available and the importance of a simple and effective predictive model.

Original languageEnglish
Article number254302
JournalPhysical Review Letters
Volume118
Issue number25
DOIs
StatePublished - 23 Jun 2017

Bibliographical note

Publisher Copyright:
© 2017 American Physical Society.

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